In the intake line system of a biochemical analyzer, in order to prevent contaminants from entering into the line system that cause failure of a variety of elements in the system, it is common to employ an intake filter to filter the water entering into the tubes so that contaminant particles in the water can be filtered. In practice, however, it has been found that if a filter with relatively high precision (the filter core has a rather small slot) is used, then when the filter is in operation, numerous bubbles will be generated on the inner wall of the filter core due to the negative pressure within the filter. After these bubbles accumulate to some extent, they will enter into the line (e.g., quantitative sampling lines of the biochemical analyzer) with the water, and reduce the precision of quantitative sampling, thereby affecting the overall testing performance of the biochemical analyzer. In order to avoid generating numerous bubbles, it is necessary to employ a filter with relatively lower precision. In this case, however, the water filtered by the filter usually contains larger contaminant particles that will choke the precise hydraulic elements, thereby disabling the hydraulic path.